Irradiation strength

In air, PTFE has a damage threshold of 200—700 Gy (2 x 10 — 7 x 10 rad) and retains 50% of initial tensile strength after a dose of 10" Gy (1 Mrad), 40% of initial tensile strength after a dose of 10 Gy (10 lad), and ultimate elongation of 100% or more for doses up to 2—5 kGy (2 X 10 — 5 X 10 rad). During irradiation, resistivity decreases, whereas the dielectric constant and the dissipation factor increase. After irradiation, these properties tend to return to their preexposure values. Dielectric properties at high frequency are less sensitive to radiation than are properties at low frequency. Radiation has veryHtde effect on dielectric strength (86). 

Polydioxanone (PDS) is completely elirninated from the body upon absorption. The mechanism of polydioxanone degradation is similar to that observed for other synthetic bioabsorbable polymers. Polydioxanone degradation in vitro was affected by gamma irradiation dosage but not substantially by the presence of enzymes (39). The strength loss and absorption of braided PDS, but not monofilament PDS, implanted in infected wounds, however, was significantly greater than in noninfected wounds. 

Properties. Most of the alloys developed to date were intended for service as fuel cladding and other stmctural components in hquid-metal-cooled fast-breeder reactors. AHoy selection was based primarily on the following criteria corrosion resistance in Hquid metals, including lithium, sodium, and NaK, and a mixture of sodium and potassium strength ductihty, including fabricabihty and neutron considerations, including low absorption of fast neutrons as well as irradiation embrittlement and dimensional-variation effects. Alloys of greatest interest include V 80, Cr 15, Ti 5... 

Fig. 12. Neutron irradiation-induced strength changes for GraphNOL N3M at irradiation temperatures of 600 and 875°C [61].

The influence of the gel content in polyisoprene-tackifier blends on creep resistance and peel behaviour have been recently studied [62]. The gel content was achieved by cross-linking the adhesives with electron beam irradiation. The molecular weight of the soluble fraction in the blend was always dominated by that of the initial elastomer. Creep resistance was achieved either through molecular weight increases or gel content increases. However, the peel strength is strongly... 

Figure 10 (a) Percent elongation at break (Cb), and (b) tensile strength (o-b) versus irradiation time for polystyrene films O-control -2,4-DHBP -2H-4MBP -2H-4BBP X-DHBP-F A-HMBP-F and Q-HBBP-F. 

Figure 11 (a) Tensile strength (TS), and (b) elongation at break (EB) versus irradiation time for PMMA films X-control ... 

The peel strength of soldered lap joint specimens was also not affected by irradiation. For example, the initial peel strength of a lap joint, fabricated from the 43 kg (95 lb) MR-TU, No. 25 tinplate, and the... 

The metallurgical experiments showed that the beta-alpha transition of the tin coating did not occur at irradiation doses of 3-5 Mrad and 6-7.5 Mrad at 5, —30, and —90°C and that the tensile properties, impact ductility, peel strength of soldered lap joints, and microstructure of commercial tinplate and solder were not affected by the irradiation conditions that are used in the sterilization of meat products. 

This paper describes an irradiation curing method which improves the mechanical, chemical, and thermal properties of multilayered flexible materials, increases the bond strength among the adhesively bonded layers, and provides flexible packages that can withstand the thermo-... 

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